Method and apparatus for generating a radio link control protocol data unit for multi-carrier operation

ABSTRACT

Techniques and apparatus for efficiently determining the radio link control (RLC) protocol data unit (PDU) size and flexible RLC PDU creation for multi carrier operation are disclosed. An example wireless transmit/receive unit (WTRU) calculates a maximum amount of data allowed to be transmitted for a current transmission time interval (TTI) for each of a plurality of carriers, and selects an RLC PDU data field size such that each RLC PDU to be multiplexed to a medium access control (MAC) PDU matches a minimum of the maximum amount of data calculated for the carriers. The maximum amount of data may, for example, be calculated based on an applicable current grant for each carrier for the current TTI. The RLC PDU may be generated for the later TTI on a condition that an amount of data in outstanding pre-generated RLC PDUs for a particular logical channel is less than or equal to 4N times the minimum of the maximum amount of data allowed to be transmitted by the applicable current grant for the carriers for the current TTI, where N is a number of activated carriers. The maximum amount of data may be calculated based on a remaining power on each carrier.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional application No.61/172,499 filed Apr. 24, 2009, which is incorporated by reference as iffully set forth.

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

A radio link control (RLC) entity in a wireless transmit/receive unit(WTRU) and UMTS terrestrial radio access network (UTRAN) may operate ina transparent mode (TM), an unacknowledged mode (UM), or an acknowledgedmode (AM). An UM RLC entity and a TM RLC entity may be configured to bea transmitting RLC entity or a receiving RLC entity. The transmittingRLC entity transmits RLC protocol data units (PDUs) and the receivingRLC entity receives RLC PDUs. An AM RLC entity comprises a transmittingside and a receiving side. The transmitting side of the AM RLC entitytransmits RLC PDUs and the receiving side of the AM RLC entity receivesRLC PDUs.

FIGS. 1A and 1B show conventional UM and AM RLC PDU formats,respectively. The Sequence Number fields indicate the sequence number ofthe RLC PDU. The Length Indicator fields are used to indicate the lastoctet of each RLC service data unit (SDU) ending within the RLC PDU. RLCSDUs or segments of RLC SDUs are mapped to the Data field.

Conventionally, an AM RLC entity may generate RLC PDUs of a fixed sizein the uplink (UL) that is configured by the network via radio resourcecontrol (RRC) signalling. Similarly, an UM RLC entity may choose the RLCPDU size from a limited configured set of sizes.

In the Third Generation Partnership Project (3GPP) Release 7, the RLCprotocol has been extended to support flexible RLC PDU sizes in the downlink (DL), but not in the UL. In 3GPP Release 8, the flexible RLC PDUsare allowed in the UL as well so that the AM and UM RLC entities areallowed to create RLC PDUs of a flexible size in the UL.

The network may configure an uplink radio bearer in a wirelesstransmit/receive unit (WTRU) to generate RLC PDUs of a flexible sizewithin a minimum and maximum RLC PDU size, which are configured by theRRC layer. More specifically, the WTRU may segment and/or concatenateuplink RLC SDUs to create RLC PDUs larger than or equal to a minimum ULRLC PDU size and smaller than or equal to a maximum UL RLC PDU size. Ifdata to be transmitted is not large enough to create an RLC PDU of theminimum UL RLC PDU size, the RLC entity may create an AM PDU smallerthan the minimum UL RLC PDU size. This removes the need for padding in acase where the amount of available data is lower than the minimum UL RLCPDU size.

For maximum transmission efficiency, the size of the RLC PDU shouldmatch the number of bits that will be allowed to be sent over the airinterface in the current transmission time interval (TTI) for a givenlogical channel. This increases transmission efficiency and greatlyreduces layer 2 (L2) header overhead.

Under the current 3GPP specification, the RLC entity may create RLC PDUsat a given transmission opportunity based on the number of bitsrequested for the given logical channel from the medium access control(MAC) entity. The RLC entity selects the size of the data field of theRLC PDU to match the data requested for a particular logical channel bythe MAC entity. With this option, the RLC entity needs to wait until thetransmission opportunity to get the information from the MAC entity and,therefore, some latency issue may occur.

Alternatively, the RLC entity may create more RLC PDUs than what may betransmitted at the upcoming TTI. This option relaxes the processingrequirements since this effectively creates a delay between the creationof an RLC PDU and its inclusion in a MAC PDU. The size of the RLC PDU isbased on number of bits allowed to be transmitted according to thecurrent grant, scheduled or non-scheduled.

In order to further improve the wireless system throughput,multi-carrier operation is being considered in 3GPP. In multi-carrieroperation, the WTRU and the Node-B may transmit and receive via multiplecarriers.

The flexible RLC PDU creation currently handles the case where RLC PDUsare transmitted via a single carrier. The inventors have recognizedthat, with multi-carrier operation, a WTRU will have the option totransmit more than one MAC PDU in a given TTI via multiple carriers.Since the channel conditions, available power, and grant may not be thesame over the carriers, techniques for flexible PLC PDU creation formulti-carriers are required.

SUMMARY

Apparatus and methods for efficiently determining the RLC PDU size andflexible RLC PDU creation for multi carrier operation are disclosed. Inone embodiment, a WTRU is configured to calculate a maximum amount ofdata allowed to be transmitted for a current TTI for each of a pluralityof carriers, and to select an RLC PDU data field size such that each RLCPDU to be multiplexed to an MAC PDU matches a minimum of the maximumamount of data calculated for the carriers. The maximum amount of datamay be calculated, for example, based on an applicable current grant foreach carrier for the current TTI. The RLC PDU may be generated for alater TTI on a condition that an amount of data in outstandingpre-generated RLC PDUs for a particular logical channel is less than orequal to 4N times a minimum of a maximum amount of data allowed to betransmitted by the applicable current grant for the carriers for thecurrent TTI, where N is the number of activated carriers. The maximumamount of data may be calculated based on a maximum remaining power oneach carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings.

FIGS. 1A and 1B are format diagrams that show conventional UM and AM RLCPDU formats, respectively.

FIG. 2 is a block diagram that shows a wireless communication systemincluding a plurality of WTRUs, a Node B, a controlling radio networkcontroller (CRNC), a serving radio network controller (SRNC), and a corenetwork.

FIG. 3 is a functional block diagram of a WTRU and the Node B of thewireless communication system of FIG. 2.

FIG. 4 is a flow diagram of an example process for generating an RLC PDUin accordance with one embodiment.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “WTRU” includes but is notlimited to a user equipment (UE), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a computer, a sensor, a machine-to-machine (M2M)device, or any other type of device capable of operating in a wirelessenvironment. When referred to hereafter, the terminology “base station”includes but is not limited to a Node-B, a site controller, an accesspoint (AP), or any other type of interfacing device capable of operatingin a wireless environment. When referred to hereafter, the terminologies“carrier” and “frequency” will be used interchangeably and it should benoted that different systems may use different terminologies, such as“component carrier” in 3GPP long term evolution (LTE).

Even though the embodiments are disclosed with reference to controlchannels and data channels associated to 3GPP high speed packet access(HSPA), it should be noted that the embodiments are not limited to 3GPPHSPA, but applicable to any wireless communication technologies that arecurrently existing or will be developed in the future including, but notlimited to, 3GPP LTE, LTE advanced, cdma2000, IEEE 802.xx, etc. Theembodiments described herein may be applicable in any order orcombinations.

With reference to FIG. 2, an example wireless communication system 100includes a plurality of WTRUs 110, a Node B 120, a controlling radionetwork controller (CRNC) 130, a serving radio network controller (SRNC)140, and a core network 150. The Node B 120 and the CRNC 130 maycollectively be referred to as the universal terrestrial radio accessnetwork (UTRAN).

As shown in FIG. 2, the WTRUs 110 are in communication with the Node B120, which is in communication via an Iub interface with the CRNC 130and the SRNC 140, the CRNC 130 and the SRNC 140 being connected via anIur interface. Although three WTRUs 110, one Node B 120, one CRNC 130,and one SRNC 140 are shown in FIG. 2, any combination of wireless andwired devices may be included in the wireless communication system 100.

FIG. 3 is a functional block diagram of a WTRU 110 and the Node B 120 ofthe wireless communication system 100 of FIG. 2. As shown in FIG. 3, theWTRU 110 is in communication with the Node B 120 and both are configuredto determine the RLC PDU size and generate an RLC PDU for multi carrieroperation in accordance with any one of embodiments.

In addition to the components that may be found in a typical WTRU, theexample WTRU 110 includes a processor 115, a receiver 116, a transmitter117, a memory 118, and an antenna 119. The WTRU 110 (i.e., the processor115, the receiver 116, and the transmitter 117), is configured totransmit and/or receive via multiple carriers on the uplink and/or thedownlink. The memory 118 is provided to store software includingoperating system, application, etc. The processor 115 may be configuredto perform, alone or in association with software, the RLC PDU sizedetermination and an RLC PDU generation for multi carrier operation inaccordance with any one of embodiments. The receiver 116 and thetransmitter 117 are in communication with the processor 115. The antenna119 is in communication with both the receiver 116 and the transmitter117 to facilitate the transmission and reception of wireless data.

In addition to the components that may be found in a typical Node-B, theexample Node B 120 includes a processor 125, a receiver 126, atransmitter 127, a memory 128, and an antenna 129. The Node B 120,(i.e., the processor 125, the receiver 126, and the transmitter 127), isconfigured to transmit and/or receive via multiple carriers on thedownlink and/or the uplink. The processor 125 may be configured todetermine the RLC PDU size and generate an RLC PDU for multi carrieroperation in accordance with any one of embodiments. The receiver 126and the transmitter 127 are in communication with the processor 125. Theantenna 129 is in communication with both the receiver 126 and thetransmitter 127 to facilitate the transmission and reception of wirelessdata.

In accordance with one embodiment, a WTRU, (i.e., RLC entity of theWTRU), may be configured to choose one RLC PDU size, (equivalently RLCPDU data field size when taking into account header(s)), for allactivated carriers and pre-generate RLC PDUs for a current and/or laterTTI on a condition that the WTRU has data available for transmission.

The WTRU may be configured to choose the size of the data field of theRLC PDU such that each RLC PDU to be multiplexed to a MAC PDU, (e.g.,MAC-i PDU), for any of the carriers matches a maximum amount of dataallowed to be transmitted given by a minimum of applicable currentgrants across the carriers. For example, in the case where two carriers,(e.g., a primary carrier and a secondary carrier) are activated, thesize of the data field of the RLC PDU may be chosen so that each RLC PDUto be multiplexed to the MAC PDU, (e.g., MAC-i PDU), matches the minimumof:

-   -   a maximum amount of data allowed to be transmitted by an        applicable current grant on the primary uplink frequency for the        current TTI and    -   a maximum amount of data allowed to be transmitted by the        applicable current grant on the secondary uplink frequency for        the current TTI.

A grant, (i.e., a grant for enhanced dedicated channel (E-DCH)transmissions), may be configured for each carrier. The grant may be ascheduled grant and/or a non-scheduled grant. For the scheduled grant,the WTRU maintains a serving grant that it updates based on informationreceived from the network. The serving grant directly specifies themaximum power the WTRU may use on the E-DCH dedicated physical datachannel (E-DPDCH) in the corresponding TTI. The serving grant is updatedby an E-DCH absolute grant channel (E-AGCH) and a E-DCH relative grantchannel (E-RGCH). The network also provides the WTRU with thenon-scheduled grant to configure the maximum block size that the WTRUmay transmit on the E-DCH during a TTI.

The “applicable grant” corresponds to either the scheduled grant or thenon-scheduled grant depending on the logical channel. If the logicalchannel belongs to a scheduled MAC-d flow, the applicable grant for thelogical channel corresponds to a serving grant (i.e., scheduled grant).If the logical channel belongs to a non-scheduled MAC-d flow, theapplicable grant for the logical channel corresponds to thenon-scheduled grant configured for the corresponding MAC-d flow.

For dual carrier operation, non-scheduled flows may be allowed on theprimary uplink frequency and may not be allowed on the secondary uplinkfrequency. In this case, if the logical channel belongs to anon-scheduled MAC-d flow, then the RLC PDU data field size may bedetermined such that each RLC PDU to be multiplexed in the MAC PDU,(i.e., MAC-i PDU), matches the amount of data allowed to be transmittedby the non-scheduled grant for the corresponding MAC-d flow. Therefore,if the non-scheduled flows are not allowed in the secondary frequency,the RLC PDU data field size may be chosen such that it matches theminimum of:

-   -   the maximum amount of data allowed to be transmitted by the        applicable current grant (scheduled or non-scheduled) on the        primary uplink frequency for the current TTI and    -   the maximum amount of data allowed to be transmitted by the        applicable current grant on the secondary uplink frequency        (scheduled) for the current TTI.        Therefore, if the WTRU is not allowed to transmit non-scheduled        data on the secondary uplink frequency, the RLC PDU size for the        logical channel belonging to the non-scheduled MAC-d flow is        determined based on the applicable grant for the primary uplink        frequency.

When determining the RLC PDU size or the size of the data field of theRLC PDU, the size of the RLC PDU may not exceed the configured maximumRLC PDU size, and may not be lower than the configured minimum RLC PDUsize unless there is not enough data available in the buffer.

For a single carrier operation, RLC PDUs may, for example, bepre-generated if the amount of data in outstanding pre-generated RLCPDUs for a particular logical channel is less than or equal to four (4)times the maximum amount of data allowed to be transmitted by theapplicable current grant (scheduled or non-scheduled) for the currentTTI. In accordance with one embodiment, for a multi-carrier operation,the WTRU may be configured to pre-generate RLC PDUs on a condition thatthe amount of data in outstanding pre-generated RLC PDUs for aparticular logical channel is less than or equal to 4×N times theminimum of the maximum amount of data allowed to be transmitted by theapplicable current grants for the carriers for the current TTI, where Nis the number of activated carriers. For example, in dual carrieroperation, N corresponds to 2, therefore the WTRU is allowed topre-generate RLC PDU(s) if the amount of data in outstandingpre-generated RLC PDUs for the logical channel is less than or equal to8 (i.e., 4×2) times the minimum of the maximum amount of data allowed tobe transmitted by the applicable current grants across the carriers forthe current TTI. For other examples, instead of 4N, any integer multipleof the number of configured carriers may be configured.

FIG. 4 is a flow diagram of an example process 400 for generating an RLCPDU in accordance with one embodiment. A WTRU, (i.e., RLC entity of theWTRU), selects a logical channel (step 402). The logical channel may,for example, be selected according to the E-DCH transport formatcombination (E-TFC) selection rule. The WTRU may be configured todetermine whether there is data available for transmission for theselected logical channel (step 404). Optionally, this may be adetermination of a sufficient amount of data over a threshold. The WTRUmay be configured to also optionally determine whether RLC PDUpre-generation is allowed for the selected logical channel. If there isno data available and/or optionally if RLC PDU pre-generation is notallowed for the logical channel, it is then determined whether there isanother logical channel for processing (step 414). In such case, theprocess 400 either branches back to step 402 for another logical channelselection or ends based on the determination in step 414.

If there is data available for the logical channel (and optionally RLCPDU pre-generation is allowed for the selected logical channel), theWTRU in this example determines whether or not the amount data inoutstanding pre-generated RLC PDU(s) for the selected logical channel inprevious TTI(s) exceeds a configured threshold (step 406). Theconfigured threshold may, for example, be 4×N times the minimum of themaximum amount of data allowed to be transmitted by the applicablecurrent grants for the carriers for the current TTI, where N is thenumber of activated carriers. If the configured threshold is exceeded,the WTRU in this example does not allowed pre-generation of more RLCPDUs for the logical channel, and the process 400 branches to step 414to determine whether there is another logical channel. If the configuredthreshold is not exceeded, the WTRU is allowed to pre-generate RLCPDU(s) for the logical channel. Alternatively, the WTRU may beconfigured to not check if it is allowed to pre-generate RLC PDUs (i.e.step 406 may be skipped), but may continue directly with the remainingsteps (408, 410, 412) to determine the RLC PDU size and how many RLCPDUs it may create. In the case where RLC PDUs cannot be pre-generated,then the number of RLC PDUs the WTRU may pre-generate will be equivalentto one.

In pre-generating the RLC PDU(s), the WTRU in this example determinesthe type of the logical channel, (i.e., scheduled or non-scheduled), anddetermines the maximum amount of data allowed to be transmitted by theapplicable current grant on each of the carriers for the current TTI(step 408). If the logical channel belongs to the scheduled MAC flow,the applicable grant is the serving grant and if the logical channelbelongs to the non-scheduled MAC flow, the applicable grant is anon-scheduled grant configured for the corresponding MAC-d flow.Alternatively or additionally, the maximum amount of data may becalculated based on power (maximum remaining power, WTRU power headroom,or the like) on each carrier, as explained in detail below.

The WTRU in this example selects the size of the data field of the RLCPDU, (equivalently the size of the RLC PDU), so that each RLC PDU to bemultiplexed to the MAC PDU (e.g., MAC-i PDU) matches the minimum of themaximum amount of data allowed to be transmitted among the activatedcarriers for the current TTI (scheduled or non-scheduled) (step 410).

The WTRU generates at least one RLC PDU for the selected logical channelfor later TTI based on the selected RLC PDU data field size (e.g.,X_(RLC PDU size)) (step 412). The WTRU in one example determines theamount of data, (i.e., the number of RLC PDUs), to pre-generate for thelogical channel as follows. The amount of RLC PDU(s) pre-generated inprevious TTIs is referred to K_(pre-generated). The maximum amount ofdata allowed to pre-generate if no RLC PDU has already beenpre-generated (K_(max,allowed data)) may be determined by4×N×X_(RLC PDU size), where N is the number of activated carriers, andX_(RLC PDU size) is the minimum of the maximum amount of data allowed tobe transmitted by the applicable current grant (scheduled ornon-scheduled) on all carriers for the current TTI. Alternatively,X_(RLC PDU size) may correspond to the RLC PDU size the WTRU can createas determined according to any of the embodiments described herein.

The WTRU may be configured to pre-generate RLC PDUs for the logicalchannel up to the remaining available space (K_(remaining allowed)),which is calculated as follows:

K _(remaining allowed)=min(K _(available data),(K _(max,allowed data) −K_(pre-generated))),  Equation (1)

where K_(available data) is the amount of available data fortransmission for the logical channel. Optionally, the WTRU may beconfigured to calculate K_(remaining allowed) after taking into accountthe data that will be transmitted on the current TTI. More specifically,if data can or will be transmitted in the current TTI, the WTRU may beconfigured to subtract that amount of data from K_(pre-generated). Ifthe RLC PDU creation is performed after the E-TFC selection procedureand MAC-i/is PDU creation has been completed, then K_(pre-generated)contains the remaining number of bits or bytes that have beenpre-generated.

The WTRU may be configured to calculate the maximum number of RLC PDUsto be pre-generated (N_(MAX RLC PDUs)) for the logical channel asfollows:

N _(MAX RLC PDUs) =└K _(remaining allowed) /X_(RLC PDU size)┘,  Equation (2)

where └x┘ is a floor function that gives the greatest integer less thanor equal to x, and N_(MAX RLC PDUs) is a non-negative integer. This mayresult in the WTRU under-generating RLC PDUs.

Alternatively, the WTRU may be configured to calculate the maximumnumber of RLC PDUs to be generated for the logical channel as follows:

N _(MAX RLC PDUs) =┌K _(remaining allowed) /X_(RLC PDU size)┐,  Equation (3)

wherein ┌x┐ is a ceiling function which gives the smallest integergreater than or equal to x. This may result in generating slightly moreRLC PDUs.

Alternatively, the WTRU may be configured to generate N full RLC PDUs ofsize X_(RLC PDU size) where N is equivalent to└K_(remaining allowed)/X_(RLC PDU size)┘, and an additional RLC PDU ofsize equal to min(minimum RLC PDU size, mod(K_(remaining allowed),X_(RLC PDU size))).

The WTRU may be configured to pre-generate the RLC PDUs when databecomes available in the RLC entity, regardless of the logical channelswhich are being multiplexed or are allowed to be transmitted at thegiven TTI. For example, even if the WTRU is not allowed to transmitscheduled or non-scheduled transmissions in the given TTI, the WTRU maystill pre-generate RLC PDUs according to the embodiments describedherein.

Alternatively, the WTRU may be configured to pre-generate the RLC PDUsfor a particular logical channel when data becomes available in the RLCentity and the WTRU is allowed to transmit the type of data for thelogical channel at the given TTI. For example, if data becomes availablefor a logical channel configured to a non-scheduled MAC-d flow, but theWTRU is not allowed to transmit non-scheduled transmissions at the givenTTI, the WTRU may be configured to not pre-generate RLC PDUs.Alternatively, this rule may be applied to scheduled flows.Alternatively, for non-scheduled flows the WTRU may be configured topre-generate the RLC PDUs after arrival of data from a higher layer ifthe non-scheduled grant for the corresponding MAC-d flow is semi-static.

Alternatively, the WTRU may be configured to pre-generate RLC PDU(s)when data is available and the WTRU is allowed to transmit data on thegiven TTI for this logical channel according to the multiplexingrestriction based on the priority of MAC-d flows.

Alternatively, the WTRU may be configured to pre-generate RLC PDU(s)when data is available and the WTRU has been able to multiplex data onthe given TTI (e.g., data will be transmitted on this TTI from thislogical channel).

In the embodiment above, the WTRU may be configured to select the sizeof the data field of the RLC PDU, (i.e., equivalently the size of theRLC PDU), so that each RLC PDU to be multiplexed to the MAC PDU (e.g.,MAC-i PDU) matches the minimum of the maximum amount of data allowed tobe transmitted on all carriers for the current TTI (scheduled ornon-scheduled).

Alternatively, the WTRU may be configured to choose the size of the datafield of the RLC PDU such that each RLC PDU to be multiplexed to the MACPDU (e.g., MAC-i/is PDU), for any of the carriers matches the maximumamount of data allowed to be transmitted given by the maximum of theapplicable current grants for the carriers.

Alternatively, the WTRU may be configured to choose the size of the datafield of the RLC PDU such that each RLC PDU to be multiplexed to the MACPDU (e.g., MAC-i/is PDU), for any of the carriers matches the maximumamount of data allowed to be transmitted given by the sum of theapplicable current grants for the carriers. In case where the currentgrants are scheduled grants expressed in terms of the power ratio, thesum may be calculated by first summing the power ratios (in linearunits) and then determining the amount of data that may be transmittedwith the summed power ratio. Alternatively, the sum may be calculated byfirst determining the amounts of data that may be transmitted with theindividual grants and then summing these amounts of data.

Alternatively, the WTRU may be configured to choose the size of the datafield of the RLC PDU such that each RLC PDU to be multiplexed to the MACPDU (e.g., MAC-i/is PDU), for any of the carriers matches the maximumamount of data allowed to be transmitted given by the average of allapplicable grants across all carriers. In case where the current grantsare scheduled grants expressed in terms of power ratio, the average maybe calculated by first averaging the power ratios (in linear units) andthen determining the amount of data that may be transmitted with theaveraged power ratio. Alternatively, the average may be calculated byfirst determining the amounts of data that may be transmitted with theindividual grants and then averaging these amounts of data.

Alternatively, the WTRU may be configured to choose the size of the datafield of the RLC PDU such that each RLC PDU to be multiplexed to the MACPDU (e.g., MAC-i/is PDU), for any of the carriers matches a runningaverage of the maximum amount of data allowed by applicable grants byall carriers for a predetermined number of TTIs (or effective number ofTTIs in case an infinite impulse response (IIR) filter is used).

In accordance with another embodiment, the WTRU may be configured tocreate multiple sets of RLC PDUs wherein the data field size of the RLCPDU in each set is chosen to match the maximum amount of data allowed tobe transmitted by the applicable grant in each carrier. For example, ifthe WTRU is configured to communicate over two carriers, the WTRU may beconfigured to generate two sets of RLC PDUs for the two carriers,wherein the data field size of the RLC PDU in each set is chosen tomatch the maximum amount of data allowed to be transmitted by theapplicable grant in the corresponding carrier.

At any TTI the WTRU may be configured to be limited by power rather thangrant. Therefore, the WTRU may be configured to take into account theavailable power on the carriers optionally in addition to the grants indetermination of the size of the data field of the RLC PDU, (i.e., themaximum amount of data allowed to be transmitted for each carrier forthe current TTI).

In case where each carrier is configured or allocated a separate maximumpower, the WTRU may be configured to calculate, for example, the maximumremaining power allowed for E-DCH transmission on each carrier. Themaximum remaining power allowed for E-DCH transmission for each carrieris a power calculated by subtracting a power required for controlchannels, (i.e., dedicated physical control channel (DPCCH) and highspeed dedicated physical control channel (HS-DPCCH)), from the allocatedmaximum power for the carrier. The WTRU may be configured to calculatethe maximum amount of data that may be transmitted based on both theapplicable current grant and the maximum remaining power allowed forE-DCH transmission on each carrier for the current TTI. The WTRU may beconfigured to then choose the size of the data field of the RLC PDU forRLC PDU pre-generation so that each RLC PDU to be multiplexed to the MACPDU (e.g., MAC-i/is PDU), matches the minimum of the maximum amount ofdata on all carriers.

The maximum remaining power allowed for E-DCH transmission may becalculated according to the E-DCH transport format combination (E-TFC)restriction mechanism specified for multi-cell operation. Whendetermining the maximum amount of data that can be transmitted on thegiven carrier based on the normalized remaining power, the WTRU may beconfigured to determine the supported E-TFC based on the power offset ofthe MAC-d flow corresponding to the given logical channel, oralternatively based on the power offset of the higher priority MAC-dflow, or of the highest priority MAC-d flow for the type of flow (e.g.,scheduled or non-scheduled). The WTRU may be configured to also takeinto account a hybrid automatic repeat request (HARQ) offset of thecorresponding logical channel.

In case where one maximum power is configured for all carriers to beshared by all carriers, the WTRU may be configured to calculate themaximum remaining power allowed for E-DCH transmission for each carrierbased on the ratio of the serving grants on the carriers afterpre-allocating a power for non-scheduled transmissions. The WTRU may beconfigured to assume that the applicable remaining power for eachcarrier may be used by the respective carrier. Alternatively, the WTRUmay be configured to assume that half of the total available remainingpower is available for each carrier.

For example, in dual carrier operation, the WTRU may be configured tofirst pre-allocate power to one (or two) carrier(s) for non-scheduledtransmissions and then split the remaining value for scheduledtransmissions according to the serving grant ratio, (i.e., the ratio ofserving grants on the carriers). For example, if non-scheduledtransmission is not allowed on the secondary carrier, the maximumremaining power allowed for E-DCH transmission on the primary carriermay be a sum of a power pre-allocated for non-scheduled transmission anda power allocated for scheduled transmission, which is calculated basedon a serving grant ratio and a remaining value calculated by subtractingthe pre-allocated power for non-scheduled transmission and a powerrequired for control channels, (i.e., DPCCH and HS-DPCCH), from theallocated maximum power for all carriers. The maximum remaining powerallowed for E-DCH transmission on the secondary carrier may be a powerallocated for scheduled transmission that is calculated based on aserving grant ratio and a remaining value calculated by subtracting thepre-allocated power for non-scheduled transmission and a power requiredfor control channels, (i.e., DPCCH and HS-DPCCH), from the allocatedmaximum power for all carriers.

These embodiments are equally applicable to operations with more thantwo carriers such that the normalized remaining power for each carrierwill determine the maximum allowed data that can be transmitted on thatcarrier based on power.

The WTRU may be configured to determine the maximum amount of data itcan transmit based on power and grant for each carrier, K_(maxdata,x)where x corresponds to carrier number. For example, for each carrier,the maximum amount of data based on the power allocated and E-TFCrestriction for that carrier and the maximum amount of data based on theserving grant for that carrier are determined, and K_(maxdata,x) forthat carrier is the minimum of these two. The WTRU may be configured todetermine the data field size of the RLC PDU for RLC PDU pre-generationas the minimum value of K_(maxdata,x) amongst all carriers. For example,if two carriers are activated (x=1, 2), the RLC PDU size, (e.g.,X_(RLC PDU size)), for RLC PDU pre-generation may be determined as theminimum of K_(maxdata,1) and K_(maxdata,2). As previously mentioned themaximum and minimum configured RLC PDU values may also be taken intoaccount.

The power offset or the HARQ profile used to calculate the number ofbits may be determined according to the one of the embodiments describedabove.

In accordance with another embodiment, the WTRU may be configured todetermine the maximum amount of data allowed to be transmitted by theapplicable current grant on all carriers for the current TTI, (i.e.,based on the minimum (or maximum, sum, or average) of the applicablegrants on all carriers). The WTRU then determines the maximum amount ofdata allowed to be transmitted by the remaining power on all carriersfor the current TTI. The WTRU then determines the size of the data fieldof the RLC PDU that need to be pre-generated for a later TTI to be theminimum of the maximum amount of data calculated based on the applicablegrants on all carriers and the maximum amount of data calculated basedon the remaining power on all carriers.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be configured to beused in conjunction with modules, implemented in hardware and/orsoftware, such as a camera, a video camera module, a videophone, aspeakerphone, a vibration device, a speaker, a microphone, a televisiontransceiver, a hands free headset, a keyboard, a Bluetooth® module, afrequency modulated (FM) radio unit, a liquid crystal display (LCD)display unit, an organic light-emitting diode (OLED) display unit, adigital music player, a media player, a video game player module, anInternet browser, and/or any wireless local area network (WLAN) or UltraWide Band (UWB) module.

1. A method for generating a radio link control (RLC) protocol data unit(PDU) for multi-carrier operation, the method comprising: selecting alogical channel; determining whether there is data available for thelogical channel; calculating a maximum amount of data allowed to betransmitted for a current transmission time interval (TTI) for each of aplurality of carriers; selecting an RLC PDU data field size for thelogical channel such that each RLC PDU to be multiplexed to a mediumaccess control (MAC) PDU matches a minimum of the maximum amount of datacalculated for the carriers; and generating at least one RLC PDU for alater TTI based on the selected RLC PDU data field size.
 2. The methodof claim 1 performed by a wireless transmit/receive unit (WTRU) whereinthe maximum amount of data that can be transmitted on each carrier iscalculated based on an applicable current grant for each carrier for thecurrent TTI.
 3. The method of claim 2 wherein the RLC PDU is generatedfor the later TTI on a condition that an amount of data in outstandingpre-generated RLC PDUs for the logical channel is less than or equal to4N times the minimum of the maximum amount of data allowed to betransmitted by the applicable current grant for the carriers for thecurrent TTI, where N is a number of activated carriers.
 4. The method ofclaim 2 wherein the applicable current grant for a first carrier of thecurrent TTI is a non-scheduled grant on a condition that the logicalchannel belongs to a non-scheduled medium access control (MAC) flow, andthe applicable current grant for a second carrier of the current TTI isa serving grant on a condition that the logical channel belongs to ascheduled MAC flow.
 5. The method of claim 4 wherein the first carrieris a primary carrier and the second carrier is a secondary carrier, andthe non-scheduled MAC flow is allowed on the primary carrier and thescheduled MAC flow is allowed on both the primary carrier and thesecondary carrier, and the RLC PDU data field size for the logicalchannel is selected so that each RLC PDU to be multiplexed to the MACPDU matches a minimum of: a maximum amount of data allowed to betransmitted by an applicable current scheduled or non-scheduled grant onthe primary carrier for the current TTI and a maximum amount of dataallowed to be transmitted by an applicable current scheduled grant onthe secondary carrier for the current TTI.
 6. The method of claim 1wherein the maximum amount of data is calculated based on both anapplicable current grant and a maximum remaining power allowed forenhanced dedicated channel (E-DCH) transmission on each carrier.
 7. Themethod of claim 6 wherein the maximum remaining power allowed for E-DCHtransmission for a primary carrier is a sum of a power pre-allocated fornon-scheduled transmissions and a power allocated based on a servinggrant ratio of the carriers, and the maximum remaining power allowed forE-DCH transmission for a secondary carrier is a power allocated based onthe serving grant ratio of the carriers.
 8. A wireless transmit/receiveunit (WTRU) for generating a radio link control (RLC) protocol data unit(PDU) in a flexible size for multi-carrier transmission, the WTRUcomprising: a transceiver configured for wireless communication usinglogical channels via a plurality of carriers; a processor configured toselect a logical channel and to determine whether there is dataavailable for the logical channel; the processor configured to calculatea maximum amount of data allowed to be transmitted for a currenttransmission time interval (TTI) for each of a plurality of carriers;the processor configured to select an RLC PDU data field size for thelogical channel such that each RLC PDU to be multiplexed to a mediumaccess control (MAC) PDU matches a minimum of the maximum amount of datacalculated for the carriers; and the processor configured to generate atleast one RLC PDU for a later TTI based on the selected RLC PDU datafield size.
 9. The WTRU of claim 8 wherein the processor is configuredto calculate the maximum amount of data that can be transmitted on eachcarrier based on an applicable current grant for each carrier for thecurrent TTI.
 10. The WTRU of claim 9 wherein the processor is configuredto generate the RLC PDU for the later TTI on a condition that an amountof data in outstanding pre-generated RLC PDUs for a particular logicalchannel is less than or equal to 4N times the minimum of the maximumamount of data allowed to be transmitted by the applicable current grantfor the carriers for the current TTI, where N is a number of activatedcarriers.
 11. The WTRU of claim 9 wherein the processor is configured tocalculate the maximum amount of data that can be transmitted on firstand second carriers for the current TTI where the applicable currentgrant for the first carrier is a non-scheduled grant on a condition thatthe logical channel belongs to a non-scheduled medium access control(MAC) flow, and the applicable current grant for the second carrier is aserving grant on a condition that the logical channel belongs to ascheduled MAC flow.
 12. The WTRU of claim 11 where the first carrier isa primary carrier and the second carrier is a secondary carrier, and thenon-scheduled MAC flow is allowed on the primary carrier and thescheduled MAC flow is allowed on both the primary carrier and thesecondary carrier, wherein the processor is configured to select the RLCPDU data field size for the logical channel so that each RLC PDU to bemultiplexed to the MAC PDU matches a minimum of: a maximum amount ofdata allowed to be transmitted by an applicable current scheduled ornon-scheduled grant on the primary carrier for the current TTI and amaximum amount of data allowed to be transmitted by an applicablecurrent scheduled grant on the secondary carrier for the current TTI.13. The WTRU of claim 8 wherein the processor is configured to calculatethe maximum amount of data based on both an applicable current grant anda maximum remaining power allowed for enhanced dedicated channel (E-DCH)transmission on each carrier.
 14. The WTRU of claim 13 wherein theprocessor is configured to calculate the maximum amount of data wherethe maximum remaining power allowed for E-DCH transmission for a primarycarrier is a sum of a power pre-allocated for non-scheduledtransmissions and a power allocated based on a serving grant ratio ofthe carriers, and the maximum remaining power allowed for E-DCHtransmission for a secondary carrier is a power allocated based on theserving grant ratio of the carriers.